Touch screens are widely used in many portable electronic devices, for instance in PDA (Personal Digital Assistant) devices, tabletops, touch surfaces, and mobile devices. Touch screens are operable by a pointing device (or stylus) and/or by a finger. Typically the devices also comprise conventional buttons for certain operations.
Stereoscopic or 3D displays capable of displaying stereoscopic images have been developed also for portable and handheld devices. Stereoscopic displays may be used to display user interface (UI) items such that the user perceives a three-dimensional (3D) image. The introduction of stereoscopic displays also brings new challenges and possibilities for user interaction design.